In the shipment of cargo by tractor trailers and the like, cargo is typically loaded and unloaded at a dock. The trailer is backed into and abuts a pair of bumpers secured to the dock. The cargo is transferred between the trailer and the dock. Usually, fork lift trucks or similar vehicles are used to transfer the cargo.
The bumpers result in an opening or gap between the edge of the dock and the edge of the trailer. Also, the floor of the trailer is usually not level with the floor of the dock.
Dock levelers, such as manufactured by DLM, Inc. of Malvern, Ark., are used to provide a ramp to bridge the gap and to provide a `level` surface whether or not there is a height difference. Dock levelers per se are well known in the field and can be pit-mounted or edge-of-dock (recessed or flush mounted) dock levelers. Whether pit-mounted or edge-mounted, there is a commonality in function. First, the dock levelers provide for a platform or ramp which both bridges the gap between the edge of the dock and the edge of the trailer and provides a flat, uniform surface for vehicular and pedestrian traffic between the dock and the inside of the trailer. Further, the dock levelers comprise articulated plates which move between an inoperative or recessed position when not in use and an operative or extended flat position when in use. Generally, dock levelers comprise a base plate to which is secured a hinged lip plate. When in the inoperative position, the lip plate hangs downwardly from the base plate. When moving to the operative position, the base plate moves upwardly and then downwardly as the lip plate extends outwardly. In the operative position, the lip plate bridges the gap between the floor of the trailer and the dock.
When a trailer is approaching or leaving a dock it is important that the driver know the position of the dock leveler.
It is particularly important that the driver know that prior to leaving a dock that the dock is in its inoperative position. Signaling devices have been used to indicate whether a dock leveler is in its operative or inoperative position to ensure that when a trailer is leaving the dock the dock leveler is in its inoperative position. This would indicate that there are no personnel or vehicles either in the trailer or just leaving the trailer as the trailer moves away from the dock.
Present state-of-the-art signaling devices are typically electronic and sense the position of the plates in the dock leveler and provide an output corresponding to the position to the plates in the dock leveler either in their operative or inoperative position.
The present invention embodies a signaling device which is mechanically linked to the movement of a plate(s) in a dock leveler to provide a visual signal corresponding to the position of the plate(s).
Broadly the invention comprises a signaling system which is mechanically joined to a dock leveler. An arm is rotatably secured within a support. One end of the arm engages the underside of a lip plate of the dock leveler. The other end of the arm has joined thereto two signal paddles of distinct visual indicia.
In the preferred embodiment of the invention, the signal paddles are fixed to the arm 90.degree. apart. The arm is counter-balanced such that the one end of the arm is biased against the undersurface of the lip plate. When the lip plate moves from its inoperative (vertical) position to its operative (horizontal) position, the counter-balance causes the one end of the arm to travel on the underside of the lip plate while rotating the signal paddles through a path of 90.degree.. The rotation of the paddles effectively moves one paddle (the GREEN GO paddle) out of view while moving the other paddle (the RED STOP paddle) in the view or line of sight of the driver of a tractor trailer. Conversely when the lip plate moves from its operative to its inoperative position the reverse of the just described motions occurs while the one end of the arm reverses its travel against the undersurface of the lip plate while being biased against the lip plate at all times by the counterweight.